Hello everybody. This is my first post here, started in this automation world using xiaomi gateways and now I’m going full with hass, I’m really impressed for all the capabilities on this SW.
Anyway, I’m not very experienced with electronics and I was thinking if there is any possibility to make my old intercom a little bit smarter. It is a 5 wire old analgic front door intercom, which basically the wiring goes as 1. GND, 2. Voice, 3. Voice 4. Call, 5 Lock. What I want do is pretty basic I guess? When someone rings I want to get the notification on hass (to do some automations of course, but that is a different story). Right now I was able to use a “Lock” in hassio to open the 12v door, using a sonoff-tasmotta with dry contact, as basically I checked the only thing it does when you press the button is to bridge the “GND” and the “LOCK”, and basically that does the trick. But for the call from the door is different. I was measuring the voltage and I see that between GND and “CALL” there is 6V, but when someone presses the front button the voltage drops, so wondering if there is any sensor I can put together in the sonoff basic so i can measure this voltage drop and make it into an event in hass?
Yes there is. The simplest way is two 10k Ohm resistors in series. The junction of these two resistors will be 3V dropping to 0V when the call button is pressed.
Hi tom_l, appreciate your help a lot. I’m using a sonoff basic R2 (the one with cables instead of rails) I modded it following a tutorial to create a dry contact that switches with the on/off function in the sonoff. It was pretty straightforward with all the nice info out there.
So in this case you are saying this 3V (after the resistors) would need to go directly to the sonoff gpio available, and cofigure it as a switch I guess?. Like 3V will be on and 0V off (but now inverted as you suggested) Then could this operate as a separate sensor (don’t want this switch to affect the relay operation which would be the LOCK) or do I need a different sonoff?
